1. Technical Field
The present invention relates generally to computer systems, and more specifically to a computer system having a Universal Serial Bus (USB) interface. In particular, the present invention allows a computer system to be activated in response to activity generated at a USB peripheral.
2. Description of the Related Art
USB has been developed to provide a uniform electrical interface for personal computer systems peripherals. As a result, peripherals such as pointing devices, joysticks, modems, and Local Area Network (LAN) adapters equipped with a USB interface, have easier connection and lowered interface cost. Currently, up-to-date USB interfaces are developed in accordance with USB specification Revision 2.0 as promulgated by USB Implementers Forum, Inc., an Oregon non-profit corporation formed by a consortium of manufacturers of USB-related components.
USB uses a hub-based interconnect, that provides a star configuration interconnect in order to interface a potentially large number of peripherals to the main processing unit of a computer system. Hubs are used to provide an individual port for each peripheral or to provide a port for connection to another hub. Power and data signaling are incorporated within a single cable, making peripheral interfaces so convenient that wall adapters for low-power peripherals may be eliminated, and a single cable connection can be made.
Present-day computer systems provide power management to conserve power and reduce heat generated by a computer system when system activity is not required. A computer system may be set to a totally shutdown state, or may be placed in various modes known as xe2x80x9csuspendxe2x80x9d or xe2x80x9cresumexe2x80x9d, among other terms of art used to describe an operating mode in which a portion of the computer system is active waiting on a stimulus to resume full system operation. Examples of stimuli that can be detected for resuming operations are mouse movement, modem dial-in, and LAN activity.
The USB specification provides a power management feature whereby a connected USB peripheral may wake up a host computer system using a resume signaling protocol. This power management feature may only be used while USB peripheral devices are placed in a suspended mode. Since the suspended mode must be initialized by the USB software components provided by the operating system, the USB peripheral device must be connected and the operating system must be executing on the host system prior to the use of the USB peripheral to wake up the system. Thus, the wake-up feature typically cannot be used with an uninitialized device that has not been connected to the host system prior to the host system entering the suspend state. Additionally, the resume signaling mechanism provides only a simple on/off signaling with no security provision for controlling power management access.
Therefore, it would be desirable to provide an improved method and apparatus for activating a computer system in response to a stimulus from a USB peripheral.
An interface for connecting a Universal Serial Bus (USB) peripheral to a computer system includes a USB physical layer interface and a wake-up controller coupled to the USB physical layer interface. The wake-up controller includes a secondary serial interface for polling the USB peripheral so that a wake-up stimulus may be detected. The interface also includes a controllable power supply for providing power to the USB peripheral during the polling operation.
The above as well as additional objectives, features, and advantages of the present invention will become apparent in the following detailed written description.